Electric detonator



y 12, 1964 w. scHARwAcHTER 3,132,586

ELECTRIC DETONATOR Filed July 24, 1961 INVENTOR WERNER SCHARWACHTER.

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a 3,132,586 Patented May 12;, 1964 ELEcTnrc nEroNA'ron [WernerScharwachter, Spich, Germany, assignor to Dynamit Nobel, A.G.,Troisdorf, Bezirk (Iologne, Germany, a German corporation Filed July 24,1961, Ser. No. 126,149 i priority, application Germany Oct. 18, 1960Claims 2 Claims. (Cl. 102-28) This invention relates to detonators and,particularly, to that type of detonator which is activated electrically.

'Detonators as employed for setting off explosive charges are oftensubject to undesired ignition by' stray i currents, electrostaticdischarges, and atmospheric electrical potential disturbances. Numerousmethods and processes have been proposed to avoid such undesirable igni-;tion and the most successful to date for such a purpose is V the typewhich is adapted to shunt such current so that it does not affect theglow wire which is ordinarily used in the ignition circuit.Imperfections in the manufacture of 1 such devices may render uncertaintheir successful opera- '1 It is an object of this invention to providea construc- 'tion of,detonator which will positively prevent externaltion.

voltage conditions from accidentallysetting off. the detonating charge.

Other objects and advantages of the construction will be'in part obviousand'inpart pointed out hereinafter.

In'tlie drawing in which is shown a prior art construction and animproved embodiment of the invention:

. FIG. 1 is a longitudinal section of a detonator as found I: in theprior art;

United States Patent ever, since in the process of manufacture thesupporting element 24 is not always accurately made and the contact atthe edges 28 and 30 with the housing 10 is not equally effective. Inthat case, with current passing, for instance,-

from the edge 28 to the terminals and 22, there may well be a largepotential difference at the terminals to cause glow in the element 12.Accidental discharge of the detonator may then take place.

To avoid thiseifect, the construction of the support for terminals 22and 20 has been modifiedso that. in every case the path of the currentsfrom housing 10 to'either terminal will be of substantially the sameresistance. To

this end, the invention provides a support 40 which in this instance, isdiamond-shaped. As in the previous case, support 40 is ofhigh-resistance material so that'high voltages will not particularlyobstruct the flow of current therethrough, while the ordinary lowvoltages used for activating, the glow element 12'will not beparticularly ductor 1s will be conductively substantially the same as2'i's a cross section taken along the line 22 of 2 FIG. 1 looking in thedirection of the arrows;

" FIG.;3 is a longitudinal section of an improved detonator embodyingthe invention; and

FIG. 4 is a cross section taken along the line 44 of FIG. 3'looking inthe direction of the arrows.

Referring to the drawing,in FIGS. 1 and 2 are shown 7 a construction ofa detonator which has found favor in the past and which is constructedwith an enclosing outer housing 10 within which is suitably mounted anignition elementor glow Wire 12 for igniting a detonating charge 214.Glowwire 12 is provided with apair of conductors 16 and18 to which isadapted to be applied a suitable ,at'erminal 20 or 22 unequallyso thatthe difierence in. {potential between the terminals will causeactivation of' 7 element 12 In order to avoid this, in the past, thesupelectrical current from a' suitable source. Glow wire 12 is attachedto a pair of terminals 20 and 22 suitably mounted in a supporting body24 held in place within housing 10. The end of housing 10 is closed by asuitable plug 26. As heretofore constructed, the support 24 isrectangular in section and the terminals 20 and 22 are spaced apartpreferably symmetrical about the center of the support. Contact with theouter housing 10 is provided at i I opposite edges 28 and 30. n l Thehousing 10 is normally metallic and the ordinary danger is that therewill be an arc'from the housing to the glow element 12, or that insomeway current will pass to porting element 24 has been made ofconductive material of relatively high resistance so that the drop involtage between point 28 and terminal 20 would be substantially the sameas that occurring from the edge 30 to terminal 22." Thus, the efiectwould be an equal grounding through conductors 16 and 18 and nopotential diiference across :the element 12. This has not always beeneffective, how- 'trically conductive material, an ignition elementwithin the housing, a pair of electrical conductors for said elementoperatively connected to said ignition element and, 1

extending to without the housing, a support for said coni the path toconductor 16 andthe potential at these points shouldbe substantiallythesame or in any case of insuflicient difference to cause anyappreciable flow through element 12. The same condition will hold ifcorner 44 contacts the wallof housing 10 instead of corner 42. In

any case, there will be no arcing from housing 10 to either conductors16 or 18 inasmuch as the resistance through the support 40 will be lessthan across the gap.

Thus are accomplished, among others, the objects hereinbefore referredto.

I claim:

1. An electric detonator comprising a housing of elecductors ofrelatively low electrical conductivity mounted within thehousingincontact therewith, said support supporting said conductors in spacedrelation with respect to each other and with respect to' the housing byengagement of the support and conductors, the shortest distance fromeach point of contact of the housing and support to each conductor beingequal, whereby current path from said housing to each terminal is ofsubstantially the same resistance. I v

2. An electric detonator as set forth in claim 1,in

which said support has a diamond-shaped cross section and extends.axially along said housing with one pair of opposite corners, thereofcontacting the housing and the other pair of opposite corners thereofspaced from the housing, one of said conductors being supported at eachof said other pair of corners.

References Cited in the file of this patent UNITED STATES PATENTS2,974,590 Ramer Mar. 14, 1961' V FOREIGN PATENTS 961,873

Germany Apr. 11, 1957

1. AN ELECTRIC DETONATOR COMPRISING A HOUSING OF ELECTRICALLY CONDUCTIVEMATERIAL, AN IGNITION ELEMENT WITHIN THE HOUSING, A PAIR OF ELECTRICALCONDUCTORS FOR SAID ELEMENT OPERATIVELY CONNECTED TO SAID IGNITIONELEMENT AND EXTENDING TO WITHOUT THE HOUSING, A SUPPORT FOR SAIDCONDUCTORS OF RELATIVELY LOW ELECTRICAL CONDUCTIVITY MOUNTED WITHIN THEHOUSING IN CONTACT THEREWITH, SAID SUPPORT SUPPORTING SAID CONDUCTORS INSPACED RELATION WITH RESPECT TO EACH OTHER AND WITH RESPECT TO THEHOUSING BY ENGAGEMENT OF THE SUPPORT AND CONDUCTORS, THE SHORTESTDISTANCE FORM EACH POINT OF CONTACT OF THE HOUSING AND SUPPORT TO EACHCONDUCTOR BEING EQUAL, WHEREBY CURRENT PATH FROM SAID HOUSING TO EACHTERMINAL IS OF SUBSTANTIALLY THE SAME RESISTANCE.